When operating an on-vehicle disk brake lathe, it is beneficial to be able to monitor the cutting status to establish the likelihood of a continuous cut being performed. To track the cutting status of a brake lathe during the turning operation, the lathe should be provided with a system for making a determination of when tool bits of the lathe have begun actively cutting surfaces of a brake disk to machine them, as well as a determination of when such cutting, once initiated, has ceased.
Past systems for monitoring the contact of tool bits of a lathe with the surfaces of a brake disk during a turning operation have employed contact sensors to determine when the tool bits of the lathe are in contact with the disk surfaces, in order to facilitate setting an appropriate depth of cut, such as taught in U.S. Pat. No. 6,363,821. This patent teaches that such contact sensors can include electrical continuity detectors, vibration sensors, and strain sensors. Electrical conductivity sensors and vibration sensors are also taught in U.S. Publication 2005/0016338 for determining when the tool bits of a lathe are in contact with disk surfaces.
The use of an electrical conductivity sensor to determine when a cutting operation has been completed is taught in U.S. Pat. No. 6,729,212, which teaches an iterative machining technique where machining is repeated with increasing depth of cut until such time as the electrical contact between the tool bit and the disk surface is determined to be substantially constant throughout the cut.